Degradation of yarns recovered from soft-armor targets subjected to multiple ballistic impacts

Tailored interyarn friction in aramid fabrics through morphology control of surface grown ZnO nanowires

“…These properties originate from the fiber's para structure, which forms fully extended all-trans chains and a highly crystalline structure with dense hydrogen bonds [1][2][3][4][5]. The high tenacity of these fibers has led to their common use in soft body armor [6][7][8]. When the fabric is impacted by a projectile, the ballistic energy is dissipated through several failure processes; primary bond breakage of the polymer chain, secondary bond breakage (fibrillation), local yarn rupture, bowing, remote yarn failure, and yarn pullout [9].…”

Recent advances in modeling and experiments of Kevlar ballistic fibrils, fibers, yarns and flexible woven textile fabrics – a review

“…148 The ‘local’ nature of the impact event is indicated by a small degradation of the tensile properties of yarns that are extracted from a shoot pack away from the impact location. 149 Strain wave reflection, noted by Freeston and Claus, 150 at the yarn cross-overs can increase the strain level depending on the reflection coefficient. Although the length and width of the fabric are larger than the thickness, impact is a ‘local’ event causing significant transverse deformation initially, which is largely neglected by the continuum scale homogenized approaches.…”

“…For instance, a sharp nosed projectile can push through the fibers within a yarn 40 and also a projectile may 'window' through the fabric with no yarn failure 148 . The 'local' nature of impact event is indicated by a small degradation of the tensile properties of yarns that are extracted from a shoot pack away from the impact location 149 . Strain wave reflection, noted by Freeston and Claus 150 , at the yarn cross overs can increase the strain level depending on the reflection coefficient.…”

Reverse ballistics penetration of Kevlar® fabric with different indenters at different loading rates

“…In particular, previous studies have shown that at high velocities, the only dominant energy-dissipation mechanism is via tensile loading of the yarn. 2,3 Previous studies by Cunniff 3,4 and Hudspeth et al 5 have shown that the effect of aperture size is negligible above the V50 limit, indicating that the damage done at high-impact velocities tends to be localized. On the other hand, at velocities below the V50 limit, mechanisms such as inter-yarn friction, yarn-projectile friction, etc., tend to play a part in dissipating energy as well, and these mechanisms involve a much larger zone of impact.…”

“…On the other hand, at velocities below the V50 limit, mechanisms such as inter-yarn friction, yarn–projectile friction, etc., tend to play a part in dissipating energy as well, and these mechanisms involve a much larger zone of impact. The projectile geometry, in any case, accounts for differences in fabric ballistic performance, 5 which is the reason destructive testing of bullet-resistant vests is dependent on bullet type and threat level.…”